"The goal of the test launch is to prove the stability and basic technical characteristics of missiles of this kind," said defence ministry spokesman Vadim Koval.

Developed by the Chelomei Design Bureau, the RS-18 is a silo-based, liquid-propellant missile, which together with the RS-16 (SS-17) and RS-20 (SS-18) comprises the fourth generation of Russian strategic missiles.

The Russian Strategic Missile Forces are considering the possibility of extending the RS-18 missiles` service term by one year to 33 years, he added.

A source in Russia`s defence industry said RS-18 missiles are currently used to test advanced warheads designed to penetrate missile defences.